Described below is a type of integrated multi-hop wireless communication system, specifically the methods and equipment involved in performing channel aware relays in an enhanced relay cluster of a wireless communication system.
In traditional wireless honeycomb communication networks, the base station always transmits information or data directly to the transfer terminal in the cluster (MS); this type of method, which does not require relay transmission, is frequently called “single-hop” transmission. When the distance between the base station and MS is relatively long or contains obstacles, “single-hop” transmission can often attain only extremely limited communication quality, to the extent that it is necessary to reduce transmission speed in order to maintain the requisite communication quality.
For this reason, in recent years the use of “multi-hop” relay transmission methods has been suggested for use in honeycomb communication networks, thus bringing about the idea of an enhanced relay cluster. FIG. 1 depicts a type of enhanced relay cluster in a honeycomb network. As can be seen from FIG. 1, MS1 is located outside the “single-hop” range achievable by multi-hop relay supported base stations, and MS2 is located within an area affected by obstacles. These two terminals are thus unable to communicate with the base station using traditional “single-hop” methods. In the enhanced relay cluster shown in FIG. 1, however, MS1 and MS2 can communicate with the base station using a two-hop process via the relay station's (RS) RS1 relay within the cluster, and in this way expand the coverage area. Furthermore, MS3 in the cluster can also assist in communications between the RS2 relay and the base station. As the single-hop distance between any two nodes (RS2 and MS3, RS2 and base station) is very close, all nodes can transmit data at a higher speed, and can thus satisfy the demands of real-time video transmission operations for high throughput.
It can be seen from FIG. 1 that multi-hop techniques integrated with honeycomb clusters not only expand the cluster base station's coverage area and eliminate the shadow effect caused by wireless communication blind spots, but also to a certain extent increases the throughput of the entire system as a whole. The advantages of an enhanced relay cluster have spurred researchers on to the next step, to research how best to integrate multi-hop technology with wireless honeycomb communication systems. For this reason, IEEE 802.16 formed the Relay Task Group, whose purpose is to implement relays into the IEEE 802.16 system, and to provide specific proposals to be written into the IEEE 802.16j protocol. IEEE 802.16j is backwards-compatible with IEEE 802.16e, and at the same time requires relay transparency toward MS, so that once the relay is introduced, no modification whatsoever of MS is required.
The type of simple direct enhanced relay cluster implementation method introduced by the Relay Task Group manages the entire enhanced relay cluster through the base station, and is called the Centralized Implementation Proposal. In this proposal, any MS and RS in the enhanced relay cluster is controlled and managed through the multi-hop transfer relay supported base station (MMR-BS); RS itself only has a few simple media access control (MAC) capabilities, and transfers operation data in accordance with MMR-BS. Therefore, the RS production costs in this proposal are low, and the design is simple and convenient to implement. Another type of implementation proposal for enhanced relay clusters is called the Distributed Implementation Proposal. In this proposal, the RS distributed through the cluster can possess higher MAC capabilities so that, for example, RS can make use of user-defined control signal frame, and perform resource distribution and control management independently. The Distributed Implementation Proposal thus provides the entire network with more robustness and increased flexibility.
The aforementioned implementation proposals both have advantages, but each has its respective defects with respect to the channel aware relays commonly used in wireless communication systems. Channel aware relays generally refer to the use of channel status to make strategic decisions in accordance with the MS report, thereby enabling the dynamic changing of transmission strategy technology, including for example, channel aware resource allocation, self-adapting code modulation, channel aware combined automatic retransmission (H-ARQ) technology, etc. The following provides an explanation of the respective features of the Centralized Implementation Proposal and the Distributed Implementation Proposal in the implementation of channel aware relay projects in accordance with channel aware resource allocation.
FIG. 2 depicts the channel aware resource allocation situation created in the Centralized Implementation Proposal. FIG. 2 shows that as before, the cluster's MMR-BS controls the management rights for the transmission of the entire cluster's resources. Every MS (or multi-hop terminal) through the multi-hop communication link must periodically, through RS (see the hardwire uplink in FIG. 2), or directly (indicated by the dashed line) report channel information to the MMR-BS, such as channel quality information (CQI) and/or channel state information (CSI). The MMR-BS then allocates wireless resources for each MS in accordance with the gathered CQI and/or CSI, and assists RS (such as RS1) to indicate to all MS the allocated wireless resources through a downstream control signal. In such circumstances, although the RS capabilities are simple, and the production costs low, the RS must periodically send large amounts of channel information to MMR-BS, which therefore results in excessive channel use between RS and MMR-BS, which ties up respective wireless resources.
In contrast to the Centralized Implementation Method, the Distributed Implementation Method allows every distributing RS to allocate relatively stronger MAC capabilities, i.e., RS can independently carry out resource distribution for the MS within its single-hop scope. Now MS only needs to report channel information directly to RS, confirm wireless resource allocation through RS, and distribute the confirmed resources to every MS using the user-defined control information frame composition of the RS. This Distributed Implementation Method can quickly conveniently perform channel aware resource allocation with extremely low channel expenditure. However, the stronger RS autonomous MAC capabilities in this proposal mean that RS design is therefore complex, production cost relatively high, and at the same time the cooperation between each RS as well as between RS and MMR-BS, such as in transferability management, cluster management and division of resources between each RS, will also be relatively complex, and will therefore consume relative more overhead information. Because of this, the Distributed Implementation Proposal is not ideal for networks that have cost restriction requirements, or where there are limited RS node enhanced relay clusters.
From this, in terms of executing channel aware relays, both the Centralized Implementation Proposal and the Distributed Implementation Proposal cannot both cut costs and reduce channel overhead. For this reason, it is now necessary to introduce a compromise proposal to carry out the channel aware relays in enhanced relay clusters.